The present invention refers to a highly loaded bearing ring, particularly an outer ring of a roller bearing and specifically the outer ring of a support roller.
In order to prevent the sagging of rolls in rolling mills, a series of support rollers, which must transmit very high radial forces are arranged behind the rolls in the mill. Normally, these support rollers are in turn arranged via roller bearings on shafts that are fastened on the roll stand. Furthermore, due to the high load acting on the support rollers, they have outer rings of relatively large cross section. The outer rings serve at the same time as the supporting rollers. Because of the stresses applied to them, these outer rings are case hardened. As a result, a layer of hardness sufficient for resisting the stresses is produced over their entire circumference. On the other hand, the core of the outer ring remains soft, so that the danger of breakage of the outer ring is reduced.
These outer rings have been observed to plastically deform because of the high stresses, which in most cases occur at high temperatures. They deform in the manner that they develop a larger diameter in the axially central region, i.e., the ring is ovalized in axial cross section. As a result, the initially cylindrical bore surface, the roller raceway, also becomes concave, so that an uneven distribution of load results for the rollers at the places where the rollers contact the outer ring. The yield strength of the ring is exceeded locally, which produces cracks parallel to the axis on the edge of the raceway, and this may lead to breakage of the outer ring.